Image Processing Library
Windows has the composition engine now (https://github.com/Microsoft/WindowsUIDevLabs and https://msdn.microsoft.com/en-us/library/windows/apps/windows.ui.composition.compositor.aspx) along with Lumia Imaging SDK https://developer.microsoft.com/en-us/windows/featured/lumia
Woops, I pressed the wrong button and submitted this without a description. Here is the description: WP7 does not allow native access so third-party image processing libraries can't be used. It also doesn't have many of the managed image operations that are included in WPF or WinForms. It would be great if there were a WP7 API for doing simple image processing operations. Things like resizing, cropping, rotating, changing bytes-per-pixel, blitting pixels, copying pixel regions, support for png, and tiff file types, etc. would be very helpful. More advanced functionality would be even more helpful but I'll take what I can get.